Add Discord bot (moderation, filters, scheduling, roles, invites, site integration)

Standalone bot/ service (its own package.json/Dockerfile) managed entirely
through a new admin-only Discord Bot panel — token stored encrypted in the
DB and pushed to the bot process in-memory, never an env var. Built in
phases, each independently verified against a live Discord guild:

- Bot skeleton: gateway connection, internal shared-secret API, self-heals
  on its own restart by pulling config from the site
- Moderation core: /ban /kick /mute /warn /warnings + mod-log channel
- Word/invite/spam filtering with leetspeak-resistant normalization and a
  staff role/channel allowlist
- Scheduled messages: recurring (cron) and one-off channel posts
- Role assignment: button role menus, auto-role on join, temp roles,
  bulk role ops
- Auto-rotating primary invite with an audit log
- Site integration: news-publish -> Discord announce webhook, manual
  /announce, read-only /wiki search

Also fixes a pre-existing bug in both DB pools (server + bot): the mariadb
driver defaulted to timezone 'local', silently mis-serializing bound Date
params by the host's local offset instead of the DB's UTC session.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

bot/src/discord/commands/announce.command.js

@@ -0,0 +1,49 @@
+const { PermissionFlagsBits, ApplicationCommandOptionType } = require('discord.js')
+
+const siteApiClient = require('../../site/siteApiClient')
+const newsAnnounce = require('../newsAnnounce')
+
+function siteOrigin() {
+  const base = process.env.SITE_PUBLIC_URL || 'http://localhost:3000/api/v1/public'
+  return new URL(base).origin
+}
+
+module.exports = {
+  data: {
+    name: 'announce',
+    description: 'Re-post or boost an existing news item.',
+    default_member_permissions: PermissionFlagsBits.ManageGuild.toString(),
+    options: [
+      { name: 'post', description: 'News post id or slug', type: ApplicationCommandOptionType.String, required: true },
+    ],
+  },
+  async execute(interaction) {
+    const idOrSlug = interaction.options.getString('post', true)
+    await interaction.deferReply({ ephemeral: true })
+
+    const result = await siteApiClient.getNewsPost(idOrSlug)
+    if (result.maintenance) {
+      await interaction.editReply({ content: `Can't reach the site right now: ${result.message || 'maintenance mode'}` })
+      return
+    }
+    if (!result.ok) {
+      await interaction.editReply({ content: `Couldn't find that news post ("${idOrSlug}").` })
+      return
+    }
+
+    const post = result.data
+    const origin = siteOrigin()
+    try {
+      await newsAnnounce.postAnnounce(interaction.client, interaction.guildId, {
+        title: post.title,
+        excerpt: post.excerpt,
+        url: `${origin}/site/news`,
+        // image_url is stored relative — Discord embeds require an absolute URL.
+        imageUrl: post.image_url ? new URL(post.image_url, origin).toString() : null,
+      })
+      await interaction.editReply({ content: `Posted "${post.title}" to the news channel.` })
+    } catch (err) {
+      await interaction.editReply({ content: `Couldn't post: ${err.message}` })
+    }
+  },
+}